Known, in particular, from document FR 2 639 874 is a printing machine comprising a transfer device capable of displacing an item to be printed from a conveyor for supplying the item to a print station device for holding the item.
This transfer device comprises a vacuum sucker mounted on an oscillating arm capable of causing the item to be printed to pivot from a position in which its axis of revolution is horizontal to a position in which its axis of revolution is vertical. During printing, the item is kept in this vertical position by the holding device. The printing screen and the doctor blades are displaced in two perpendicular directions for printing the item.
However, the device for displacing the screen and the doctor blades is mechanically complex. Moreover, this type of printing machine has low printing rates. Furthermore, the transfer device used in this machine cannot be used in printing machines comprising a plurality of print and drying stations.
Also known, in particular from document FR 2 367 610, is a printing machine comprising a device for transferring an item between a supply conveyor and a holding device. The transfer device comprises a crank lever carried by a shaft, parallel to the axis for the take-up of the item. In its median zone, the lever carries a roller by means of which it is subjected, for the control during pivoting thereof, to a rotary cam engaged with a guide track.
In this printing machine, the screen and the doctor blades are not displaced around the item; instead, the item is displaced along a circle having a radius equal to the radius of the elliptical cross-section of the item.
However, the position for taking up the item on the supply conveyor depends on the radius of the elliptical item. Accordingly the relative position between the print station and the conveyor for supplying the item has to be modified each time the printing station is used to print an item having a differing shape or size.
Similarly, when a transfer device of this type is used for displacing a printed item between the print station and a conveyor for discharging the item, the relative position between the print station and the discharge conveyor has to be modified each time the printing machine is used to print an item of differing size or shape.
The object of the invention is to provide a printing machine which is of simple construction and easily adjustable, in particular without relative displacement of the supply and discharge conveyors, when series of items of differing size and shape have to be printed.